bpf: Introduce BPF_PROG_TYPE_LSM

Introduce types and configs for bpf programs that can be attached to
LSM hooks. The programs can be enabled by the config option
CONFIG_BPF_LSM.

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Florent Revest <revest@google.com>
Reviewed-by: Thomas Garnier <thgarnie@google.com>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: James Morris <jamorris@linux.microsoft.com>
Link: https://lore.kernel.org/bpf/20200329004356.27286-2-kpsingh@chromium.org

3 files changed, 24 insertions, 6 deletions

diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index 046ce5d98033..f2d7be596966 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -29,4 +29,5 @@ obj-$(CONFIG_DEBUG_INFO_BTF) += sysfs_btf.o
 endif
 ifeq ($(CONFIG_BPF_JIT),y)
 obj-$(CONFIG_BPF_SYSCALL) += bpf_struct_ops.o
+obj-${CONFIG_BPF_LSM} += bpf_lsm.o
 endif
diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
new file mode 100644
index 000000000000..82875039ca90
--- /dev/null
+++ b/kernel/bpf/bpf_lsm.c
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 2020 Google LLC.
+ */
+
+#include <linux/filter.h>
+#include <linux/bpf.h>
+#include <linux/btf.h>
+
+const struct bpf_prog_ops lsm_prog_ops = {
+};
+
+const struct bpf_verifier_ops lsm_verifier_ops = {
+	.get_func_proto = bpf_tracing_func_proto,
+	.is_valid_access = btf_ctx_access,
+};
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index e619eedb5919..37ffceab608f 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -779,8 +779,8 @@ static const struct bpf_func_proto bpf_send_signal_thread_proto = {
 	.arg1_type	= ARG_ANYTHING,
 };
 
-static const struct bpf_func_proto *
-tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
+const struct bpf_func_proto *
+bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
 	switch (func_id) {
 	case BPF_FUNC_map_lookup_elem:
@@ -865,7 +865,7 @@ kprobe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_override_return_proto;
 #endif
 	default:
-		return tracing_func_proto(func_id, prog);
+		return bpf_tracing_func_proto(func_id, prog);
 	}
 }
 
@@ -975,7 +975,7 @@ tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_get_stack:
 		return &bpf_get_stack_proto_tp;
 	default:
-		return tracing_func_proto(func_id, prog);
+		return bpf_tracing_func_proto(func_id, prog);
 	}
 }
 
@@ -1082,7 +1082,7 @@ pe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_read_branch_records:
 		return &bpf_read_branch_records_proto;
 	default:
-		return tracing_func_proto(func_id, prog);
+		return bpf_tracing_func_proto(func_id, prog);
 	}
 }
 
@@ -1210,7 +1210,7 @@ raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	case BPF_FUNC_get_stack:
 		return &bpf_get_stack_proto_raw_tp;
 	default:
-		return tracing_func_proto(func_id, prog);
+		return bpf_tracing_func_proto(func_id, prog);
 	}
 }